Auxiliary artificial heart of an embedded type

ABSTRACT

An artificial heart has a driving section, a nozzle section, a pump section for insertion into a ventricle of a human heart, and a sealing section forming a seal for a driving shaft extending from the driving section for driving the pump section. A sealing liquid chamber filled with a sealing liquid is formed around the driving shaft between the sealing mechanism and the driving section. The sealing liquid in the sealing liquid chamber maintains the sealing mechanism in a liquid-tight state and lubricates the sealing mechanism, whereby blood is prevented from entering the driving section. Even if blood happens to enter the driving section, the blood is mixed with the sealing liquid and does not coagulate. Thus, the operation of the artificial heart is not suppressed.

RELATED APPLICATIONS

This a divisional of application Ser. No. 09/469,290, filed Dec. 22,1999, now U.S. Pat. No. 6,302,910, which is a divisional of applicationSer. No. 08/603,193, filed Feb. 20, 1996, now abandoned, which is acontinuation-in-part of application Ser. No. 08/505,784, filed Jul. 21,1995, now abandoned, which is a continuation-in-part of application Ser.No. 08/079,817, filed Jun. 22, 1993, now abandoned, the disclosures ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an auxiliary artificial heart of an embeddedtype, embedded in the left or right ventricle of the heart in a humanbody, and more particularly to an artificial heart operated at highreliability by preventing body fluids such as blood from adverselyentering the artificial heart.

2. Description of the Related Art

Conventional artificial hearts are of the diaphragm type, sack type,axially symmetric type, centrifugal type, of pusher plate type or thelike. Each of these conventional artificial hearts delivers blood inplace of a human heart or by bypassing it.

Recently, an auxiliary artificial heart has been developed which isembedded in a ventricle of a human heart and has the tip end of a nozzlepassing through an aorta valve or the like such that blood is deliveredfrom the ventricle into an aorta through the nozzle. The artificialheart does not suppress any function of the human heart when it isinstalled in the human heart and it delivers additional blood into theaorta when blood pumped out from the human heart is insufficient. Theblood is delivered not only by the artificial heart but also by thepulsing or beating of the human heart. Even if the operation of theartificial heart happens to stop, blood is delivered to the body bybeating of the human heart.

Naturally, the volume of the part of the artificial heart which isinserted in a ventricle of the human heart must be smaller than thevolume of the human heart when it is fully contracted. Such anartificial heart has a pump body comprising a cylindrical axial-flowpump section, a nozzle section provided on its distal end and a drivingsection provided on the proximal end of the axial-flow pump section. Thecardiac apex of a ventricle of a human heart is cut and a shortcylindrical cardiac apex ring is embedded therein. The pump section andthe nozzle section are inserted in the ventricle through the cardiacapex ring, and the distal end of the nozzle section is inserted in anaorta through its aorta valve or the like. The driving section which hasa large volume is embedded in a portion of the thorax which is outsideof the human heart.

The artificial hearts has the following problem in connection with thefunction of a shaft-sealing mechanism provided between the pump sectionand the driving section. With the artificial heart, a motor and otherelements are housed in the driving section, and the rotor of the pumpsection is driven via a driving shaft extending from the driving sectionto the pump section. Blood supplied by systemic blood pressure flowsthrough the pump section. In this arrangement, blood is not allowed toenter the space in the driving section. If blood enters the spacedefined in the driving section, coagulation of blood occurs and theoperation of the motor stops.

It is necessary to provide, between the driving section and the pumpsection, a sealing mechanism for sealing the driving shaft in a liquidtight state in order to prevent blood from entering the interior of thedriving section. Since, however, the artificial heart is embedded in ahuman body, the artificial heart must be operated for a long timewithout maintenance. It is not easy with the present technology toprovide a shaft-sealing mechanism with which perfect sealing ismaintained for a long time.

SUMMARY OF THE INVENTION

The object of this invention is to provide an artificial heart which hasa shaft-sealing mechanism for completely preventing blood from enteringthe interior of a driving section for a long time.

An auxiliary artificial heart according to this invention inserted in aventricle of a human heart, including a cylindrical cardiac apex ringembedded in the cardiac apex of the human heart by cutting the cardiacapex, and a main body of the artificial heart comprising a cylindricalaxial flow pump section inserted in the ventricle of the human heartthrough the cardiac apex ring, a nozzle section extending outward fromthe distal end of the pump section through the aorta valve of the humanheart and a driving section provided on the proximal end of the pumpsection and disposed outside (or externally) of the human heart, fordriving the pump section through a driving shaft.

Between the driving section and the pump section is provided a sealingmechanism for maintaining the driving shaft in a liquid tight state toprevent blood from entering the interior of the driving section from thepump section. The sealing mechanism defines a sealing liquid chambersurrounding the driving shaft at the driving section and a sealingliquid is filled in the sealing liquid chamber.

According to a preferred embodiment, the sealing liquid includes aphysiological sodium chloride solution or an anticoagulant such asheparin, and the sealing liquid chamber communicates with a sealingliquid bag made of flexible material, filled with the sealing liquid andembedded in the human body.

The sealing mechanism is provided with an oil seal made of elasticmaterial, closely fitted on the outer peripheral surface of the drivingshaft due to its elastic deformation and forming a lubricating film ofthe sealing liquid between the peripheral surface of the driving shaftand the oil seal.

The pump section is driven by a motor or the like driving unit housed inthe driving section. The pump section sucks blood from a ventricle of ahuman heart and discharges it into an aorta from the nozzle section ofthe distal end of the pump section by bypassing the aorta valve or thelike. Thus, blood is delivered to the aorta not only by the beating ofthe human heart but also by means of the artificial heart. Theartificial heart supplements any insufficient amount of blood which isnot provided by the human heart, whereby it is ensured that thenecessary amount of blood can be delivered. The volume of the pumpsection is smaller than the volume of the ventricle of the human heartwhen it contracts most so as not to interfere with natural beating ofthe human heart.

The sealing mechanism prevents blood from entering the driving sectionfrom the pump section. In this case, the sealing mechanism defines asealing liquid chamber at the driving section, and a sealing liquid suchas a physiological sodium chloride solution fills the sealing liquidchamber. Sealing and lubrication of the sealing mechanism are ensured bythe sealing liquid, and blood is securely prevented from entering theinterior of the driving section from the sealing mechanism.

Even if the sealing mechanism is deteriorated and blood enters themechanism, the blood which has entered the mechanism is mixed with thesealing liquid. Thus, blood is not coagulated and does not prevent thesmooth operation of the artificial heart.

In the embodiment, the sealing mechanism is provided with an oil sealwhich forms a lubricant film of the sealing liquid between the oil sealand the outer peripheral surface of the driving shaft and is elasticallyclosely fitted on the outer peripheral surface of the driving shaft forsecurely preventing the entrance of blood such that the oil seal is notworn and is durable. The oil seal can be designed such that thelubricant film formed between the oil seal and the outer peripheralsurface of the driving shaft delivers blood in only one direction towardthe pump section. This structure prevents blood from entering theinterior of the driving section.

According to the preferred embodiment, the sealing liquid chambercommunicates with the sealing liquid bag embedded in the human thorax orother location. A sealing liquid is supplemented from the sealing liquidbag and thus can be supplied to the sealing liquid chamber for a longtime.

In a preferred embodiment, the driving shaft uses a dynamic pressurebearing made of ceramic material operated in the sealing liquid. Acoating film is formed between the sliding surfaces due to the dynamicpressure of the sealing liquid, thereby reducing rotational resistanceof the bearing and preventing wear, leading to high reliability.

When the driving shaft is rotated, the dynamic pressure bearinggenerates dynamic pressure. The dynamic pressure provide a liquid sealbetween the sealing liquid chamber and the driving section. The sealingliquid is thereby prevented from flowing from the sealing liquid chamberinto the driving section.

The dynamic pressure bearing, which is mounted on the distal end portionof the driving shaft, supplies the sealing liquid to the oil seal.Hence, the sealing liquid circulates in the artificial heart, preventingforeign bodies from depositing.

In a further preferred embodiment, a metal plating is formed on theouter peripheral surface of the driving shaft. Tetrafluoroethylene andits derivatives are made eutectic in the metal plating film, therebyimproving not only lubricating properties between the driving shaft andthe oil seal but also durability.

The metal plating film of this kind is water-repellent and is wellcompatible with the living body. Any component that contacts blood orother body fluid may be covered entirely with such a metal plating film.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a cross-sectional view of an artificial heart of a firstembodiment of this invention, provided in the left ventricle of a humanheart;

FIG. 2 is a longitudinal cross-sectional view of the main body of theartificial heart of the first embodiment;

FIG. 3 is a cross-sectional view of a sealing section;

FIG. 4 is an enlarged cross-sectional view showing the structure of afilm formed on the outer peripheral surface of a driving shaft;

FIG. 5 is an exploded view of one of two dynamic pressure bearings;

FIG. 6 is an exploded perspective view of the other dynamic pressurebearing;

FIG. 7 is a diagram showing the dynamic pressure bearing, as viewed inthe direction of arrows 7 in FIG. 5;

FIG. 8 is a diagram showing the dynamic pressure bearing, as viewed inthe direction of arrows 8 in FIG. 5;

FIG. 9 is a sectional view taken along line 9 in FIG. 8;

FIG. 10 is a longitudinal cross-sectional view of another embodiment ofthe dynamic bearing;

FIG. 11 is a longitudinal cross-sectional view of a further embodimentof the dynamic bearing;

FIG. 12 is a longitudinal cross-sectional view of the main body of anartificial heart of a second embodiment according to this invention;

FIG. 13 is a longitudinal cross-sectional view of the main body of theartificial heart of a third embodiment according to this invention;

FIG. 14 is an enlarged longitudinal cross-sectional view of part of FIG.13;

FIG. 15 is a longitudinal cross-sectional view of the main body of anartificial heart according to a further embodiment of the presentinvention;

FIG. 16 is a cross-sectional view illustrating the bearing tube, seatring and follow ring forming part of a sealing mechanism for theembodiment of FIG. 15;

FIG. 17 is an elevational view of the drive shaft and bearings therefor;

FIG. 18 is a longitudinal cross-sectional view of a main body of anartificial heart according to a still further embodiment hereof;

FIG. 19 is a fragmentary longitudinal cross-sectional view of thesealing mechanism of the embodiment illustrated in FIG. 18; and

FIG. 20 is a view similar to FIG. 19 illustrating a further form ofsealing mechanism.

FIG. 21 shows the state of an artificial heart having a centrifugal pumpembedded in a body cavity;

FIG. 22 is a longitudinal cross-sectional view of the main body of theartificial heart of a seventh embodiment;

FIG. 23 is a longitudinal cross-sectional view of the main body of theartificial heart of an eighth embodiment;

FIG. 24 is a longitudinal cross-sectional view of the mechanism of aninth embodiment;

FIG. 25 is a longitudinal cross-sectional view of the mechanism of atenth embodiment; a longitudinal cross-sectional view of the

FIG. 26 is a longitudinal cross-sectional view of the mechanical sealmechanism of an eleventh embodiment;

FIG. 27 is a longitudinal cross-sectional view of the mechanical sealmechanism of a twelfth embodiment;

FIG. 28 is a longitudinal cross-sectional view of the main body of theartificial heart of a thirteenth embodiment; and

FIG. 29 is a longitudinal cross-sectional view of the mechanical sealmechanism of a fourteenth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments of this invention will be described with reference theaccompanying drawings.

A first embodiment of this invention is shown in FIGS. 1 to 6. FIG. 1shows an artificial heart of this invention embedded in the leftventricle B of the heart A of a patient (hereinafter referred to as the“human heart”). A cardiac apex, a left atrium, a mitral valve, an aortavalve and an aorta are designated by C, D, E, F and G, respectively.

The artificial heart 1 comprises a cardiac valve ring 2 and the mainbody 3 of the artificial heart. The cardiac valve ring 2 is a shortcylindrical member having a flange and is embedded in the human heart Athrough the cardiac apex C of the human heart A after the cardiac apex Chas been cut. The main body 3 of the artificial heart 1 comprises a pumpsection 4, a nozzle section 6 provided on the distal end of the pumpsection 4 and a driving section 5 provided on the proximal end of thepump section 4. The pump section 4 and the nozzle section 6 are insertedin the left ventricle B through the cardiac apex ring 2, and the nozzlesection 6 is further inserted in the aorta G through the central portionof the aorta valve F. Liquid tightness is ensured between the cardiacapex ring 2 and the main body 3 by means of a sealing mechanism, forexample, a sealing member 8.

The pump section 4 is a relatively small cylindrical member and it has asmaller volume than the volume of the left ventricle B when it contractsmost so as not to prevent natural beats of the human heart A. In thepump section 4 is housed a small axial-flow pump which is driven by amotor provided in the driving section 5. The pump section 4 sucks bloodfrom the left ventricle B at a suction port 7 formed in the outerperipheral surface of the section 4 and discharges the blood from thedistal end of the nozzle section 6 into the aorta G with the aorta valveF bypassed.

The nozzle section 6 passing through the central portion of the aortavalve F is made of soft synthetic resin material that does not suppressthe function of the aorta valve F and it does not injure the aorta valveF.

The driving section 5 is embedded in a portion of the thorax outside ofthe human heart A. In the driving section 5 are provided a motor andother elements such as electric cells and electronic control elements ifthey are required. The driving section 5 is connected by means ofelectric wires 9 to a non-contact type electrode 10 embedded in aportion of the human body close to the patient's skin H. A necessaryelectric power is supplied from an external electric source (not shown)to the driving section 5 through the electrode 10.

The driving section 5 is further connected to a sealing liquid bag 12 bya flexible tube 11. The sealing liquid bag 12 is made of flexiblematerial and filled with a sealing liquid such as a physiological sodiumchloride solution. The sealing liquid bag 12 is embedded in a suitableportion of the body of the patient, such as the thorax or the abdominalcavity.

The structure of the main body 3 will be described with reference toFIG. 2. The pump section 4 has a cylindrical casing 21 which is reducedin diameter at its distal end portion to form the nozzle section 6 andis connected at its proximal end portion to the driving section 5 by anextension 24. In the casing 21 are provided an axial-flow pump such as apropeller 22 and a plurality of guide vanes 23 for directing the bloodflow. The suction port 7 is formed in the outer peripheral surface ofthe casing 21. In the casing 21 is formed a continuous blood passageextending from the suction port 7 to the nozzle section 6 via thepropeller 22 and the guide vanes 23. A thin cylindrical nozzle tube 25made of flexible synthetic resin material is mounted on the nozzlesection 6. As described above, the nozzle tube 25 is designed to improvethe contacting properties of the nozzle tube 25 with the ventricle valveF, prevent injury of the ventricle valve F and prevent suppression ofthe function of the ventricle valve F. The nozzle tube 25 is a flexiblethin cylindrical member. Thus, when the artificial heart happens to beout of order, the nozzle tube 25 is collapsed by the blood pressure inthe aorta G so as to act as a check valve for preventing blood fromflowing backward from the aorta G to the left ventricle B.

The distal end portion of the driving shaft 26 is connected to thepropeller 22. The driving shaft 26 passes through the extension 24 andextends to the interior of the driving section 5. In the driving section5 is provided a motor having a stator coil 32 and a rotor 33. Theproximal end portion of the driving shaft 26 is connected to the rotor33. A cover 34 seals the driving section 5 hermetically.

In this embodiment, the blood flow passage in the pump section 4 is madesmooth. The center portion of the pump section 4 has a boss portion 61,in which the driving shaft 26 and the bearing 28 are inserted. Thesealing mechanism 31 is located in the distal end of the boss section61, and has a conical oil seal. The oil seal is fitted in the conicaldepression formed in the rear end of a propeller boss 63 of thepropeller 22, with a small gap formed between the oil seal and theconical depression. The guide vane 23 has a boss 64 which opposes thefront end of the propeller boss 63 and is located a short distancetherefrom. No steps are made between the inner peripheral surface of thecasing 21 and the outer surfaces of the boss section 61, propeller boss63 and boss 64. A smooth annular blood flow passage is therefore formedbetween the inner peripheral surface of the casing 21 and the outersurfaces of the components 61, 63 and 64.

The suction port 7 is formed in the proximal part of the boss section61. A plurality of flow regulating vanes 62 are arranged between thesuction port 7 and the propeller 22.

Since the blood flow passage is smooth as described above, the blood canflow smoothly, enhancing the pump's efficiency and reducing the numberof places where the blood does not flow. Hence, the possibility ofthrombi is decreased.

The distal end portion of the driving shaft 26 is supported by a bearing28 made of ceramic material, and the proximal end portion of the drivingshaft 26 is supported by dynamic pressure bearings 35 and 36 made ofceramic material in the driving section 5. On the distal end portion ofthe driving shaft 26 is provided a sealing mechanism 31 for performingsealing between the interior of the pump section 4 and the interior ofthe driving section 5 such that blood in the pump section 4 is preventedfrom entering the driving section 5.

In the portion of the main body 3 between the sealing mechanism 31 andthe driving section 31 (for example, the extension 24 of the casing 21)is formed a sealing liquid chamber 30 surrounding the driving shaft 26.A sealing liquid such as a physiological sodium chloride solution isfilled in the sealing liquid chamber 30. If necessary, a blood coagulantsuch as heparin or any other chemical agents, if required are added tothe sodium chloride solution.

The sealing liquid is not limited to physiological chloride solution.Heparin solution may be used as sealing liquid.

An axial groove 37 is formed between the outer wall 38 and dynamicpressure bearing. The space is filled with the sealing liquid andsubstantially forms part of the sealing liquid chamber 30. Between theouter peripheral surface of the dynamic pressure bearing 35 and theinner peripheral surface of the casing 31 is formed an axial groove 37which communicates with the sealing liquid chamber 30 and a narrowpassage 38 formed in the inside wall of the driving section 5. Thesealing liquid chamber 30 communicates with the sealing liquid bag 12via the groove 37, the passage 38 and the tube 11.

The sealing mechanism 31 will be described. In this embodiment, an oilseal is used as the oil seal 31. The oil seal is made of elasticmaterial such as synthetic rubber, and has an elastically deformable lipportion which abuts against the outer peripheral surface of the drivingshaft 26 to maintain liquid tightness. The oil seal has a specificfeature in that a lubricating film of the sealing liquid is formedbetween the oil seal itself and the drive shaft 26. This lubricatingfilm ensures sealing and prevents direct contact of the oil seal withthe outer peripheral surface of the driving shaft 26 such that the oilseal is free from wear for a long time.

In FIG. 3 is shown an preferred embodiment of the seal mechanism 31provided with an oil seal 41 made of synthetic rubber, for example, andhaving a elastically deformable lip portion 42. The inner peripheralsurface of the lip portion 42 is in contact with the outer peripheralsurface of the driving shaft 26. A garter spring 43 is provided on theoil seal, for stabilizing contact pressure between the lip portion 42and the outer peripheral surface of the driving shaft 26. As describedabove, the oil seal 42 is designed such that a thin lubricating film ofthe sealing liquid is formed between the inner peripheral surface of thelip portion 42 and the outer peripheral surface of the driving shaft 26.The sealing liquid acting as the lubricating film is adapted tocirculate on the sealing surface by the rotation of the driving shaft26.

Further, in this embodiment, the sealing liquid acting as thelubricating film is adapted to flow in only one direction toward thepump section 4 so that the sealing liquid flows little by little throughthe pump section 4. This behavior of the sealing liquid securelyprevents blood from entering, from the pump section 4, the sealingsurface defined between the oil seal 41 and the driving shaft 26.

Since the sealing liquid is a sodium chloride solution and a very smallamount of the solution flows into the pump section 4, it does not affectthe human body. It is sufficient that the amount of the flowing-outsealing liquid is several cubic centimeters per month, for example, andthe amount of the sealing liquid corresponding to the discharged amountis supplied from the sealing liquid bag 12. When, therefore, several toten cubic centimeters of the sealing liquid is contained in the sealingliquid bag 12, it is unnecessary to supplement the sealing liquid formore than a year.

The oil seal 41 may be made of various materials. Examples of thematerials are: silicone rubber, urethane rubber, ethylene-propylenerubber, nitrile rubber, fluororubber, acrylic rubber, natural rubber,fluororesin, polytetrafluoroethylene, polyurethane, and the like.

A coating is formed on the outer peripheral surface of the driving shaft26 in order to improve lubricating properties between the oil seal 41and the driving shaft 26 and enhancing durability. The coating will bedescribed with reference to FIG. 4.

The oil seal 41 is elastically closely fitted on the outer peripheralsurface of the driving shaft 26 to prevent blood entrance. Surfacetreatment is required on the driving shaft 26 so as to maintain thesealing function of the oil seal 41 for a long time. This is because thedriving shaft 26 also needs to have good lubricating properties,wear-resistance, and durability. In this embodiment, a compound platingfilm 52 is formed on the surface of the driving shaft 26. The compoundplating film 52 is formed by making a great number oftetrafluoroethylene fine particles 51 distributed evenly in anelectroless nickel plating film so as to be eutectic. In the embodiment,the eutectic amount of tetrafluoroethylene is about 25%.

The driving shaft 26 is made of stainless steel, for example. Aftercleaning (or removing oily material) and activating, nickel isflush-plated on the driving shaft 26. Thereafter, a nickel-plated filmhaving a thickness of several micrometers is formed in anickel-phosphorus plating solution in which there are distributedtetrafluoroethylene fine particles which have been made hydrophilic by asurface active agent. By this treatment, fine particles 57 oftetrafluoroethylene are made eutectic in the nickel plating film, and acompound plating film 58 is formed as shown in FIG. 4.

When the base material of the driving shaft 26 is hardened by heattreatment, the compound plating film 52 provides Vickers hardness of 500to 600. Since fine particles 57 of tetrafluoroethylene are exposed onthe surface of the compound plating film 58, they provide goodlubricating properties and water-repellent properties. Fine particles 57of tetrafluoroethylene is suited for human bodies well. The fineparticles 57 are held in the nickel plating film and are combinedtogether. Thus, the fine particles 57 are held firmly so as not to falloff the plating film.

The compound plating film 58 is water-repellent, prevents coagulation ofblood, and is compatible with the living body. The film 58 may be formednot only on the outer peripheral surface of the driving shaft 26 whichcontacts the oil seal 41, but also on the other components of theartificial heart which contact blood and/or other body fluids.

The sealing mechanism 31 is not limited to an oil seal but can beapplicable to the other sealing mechanism such as a labyrinth packing,if the conditions allow.

A dynamic pressure bearing assembly will be described with reference toFIG. 5. The dynamic pressure bearing assembly rotatably supports theproximal end portion of the driving shaft 26 and performs sealingbetween the sealing liquid chamber 30 and the space in the drivingsection 5, as well.

The dynamic pressure bearing assembly comprises an outer fixed-sidebearing 35 and an inner rotary-side bearing 36 which are made of ceramicmaterial. The fixed-side bearing 35 and the rotary-side bearing 36 havecylindrical portions 35 a and 36 a and flange portions 35 b and 36 b,respectively. The cylindrical portion 36 a of the rotary-side bearing 36is closely fitted in the cylindrical portion 35 a of the fixed-sidebearing 35, and the flange portions 35 a and 35 b are in a close contactwith each other.

A plurality of dynamic-pressure generating grooves 51 and 52 are formedin the outer peripheral surface of the cylindrical portion 36 a of therotary-side bearing 36 and the contacting surface of its flange portion36 b.

The abutting surface of the flange portion 35 b of the fixed-sidebearing 35 is flat as illustrated in FIG. 7. A plurality ofdynamic-pressure generating grooves 52 are formed in the abuttingsurface of the flange portion 46b of the rotary-side bearing 36 as shownin FIG. 8. The grooves 52 are curved as shown in FIG. 8. They areshallow as illustrated in FIG. 9, about 3 to 10 microns deep. Thoseportions of the surface, or the lands 36 c located among the grooves 52,and the surface of the flange portion 35 b of the fixed-side bearing 35is smooth, having undulation of 0.3 microns or less and maximumroughness of about 0.1 micron. The dynamic-pressure generating grooves52 have been formed by shot blasting the abutting surface of the flangeportion 46 b.

A pair of dynamic-pressure generating grooves 51 are formed in the outerperipheral surface of the cylindrical portion 36 a of the rotary-sidebearing 36. These grooves 51 are shaped like a herringbone and have thesame depth as the dynamic-pressure generating grooves 52 formed in theabutting surface of the flange portion 46 b. The grooves 51 extend inthe opposite directions. Hence, when the driving shaft 26 is rotated,they guide the sealing liquid in the opposite directions.

The operation of the dynamic pressure bearings 35 and 36 will bedescribed.

When the driving shaft 25 is rotated, the rotary side bearing 36 isrotated, too. The sealing liquid is thereby is supplied from thedynamic-pressure generating grooves 52 toward the center of the flangeportion 36 b, guided along the dynamic-pressure generating grooves 51formed in the abutting surface of the flange portion 36 b. The sealingliquid is simultaneously supplied to the middle portion of thecylindrical portion 36 a, also along the dynamic-pressure generatinggrooves 51.

As a result, a layer of sealing liquid is formed under high pressure atthe center of the flange portion 36 b. Located between the fixed-sidebearing 35 and the rotary-side bearing 36, the sealing liquid layerprevents a mechanical contact between the bearings 35 and 36. It servesas lubricant, enabling the rotary-side bearing 36 to rotate with anextremely low resistance applied to it, and preventing wear of thebearing 36. The cylindrical portion 36 a and flange portion 36 b of therotary-side bearing 36 bear the radial load and thrust load exerted bythe driving shaft 26, respectively.

Since the dynamic-pressure generating grooves 51 and 52 guide thesealing liquid under high pressure to the center of the flange portion36 b and the middle portion of the cylindrical portion 36 a, the liquidreliably serves as lubricant though the liquid itself has poorlubrication action.

Both the fixed-side bearing 35 and the rotary-side bearing 36 are madeof a hard ceramic material such as sintered SiC, sintered α-SiCcontaining BeO, or sintered Si₃N₄. The ceramic materials exemplified arevery hard and have a small coefficient of friction. No wear occursbetween the bearings 35 and 36 even if they directly contact each otherwhen the motor is started or stopped or while the motor shaft isrotating.

In FIG. 6 is shown the bearing 28 which comprises a rotary-side bearing28 a and a fixed-side bearing 28 b. A pair of dynamic-pressure grooves70 similar to the dynamic-pressure grooves 51 are formed in the outerperipheral surface of the rotary-side bearing 28 a. By the paireddynamic-pressure grooves 70, the sealing liquid is delivered in theopposite directions and a sealing liquid film is formed between theouter peripheral surface of the rotary-side bearing 28 a and the innerperipheral surface of the fixed-side bearing 28 b. The sealing liquidfilm reduces resistance of rotation, prevents wear and improvesdurability.

The bearing 28 may have a structure as shown in FIG. 10. A plurality ofdynamic-pressure generating grooves 71 are formed in the outerperipheral surface of the rotary-side bearing 28 a. Each of thesegrooves 71 consists of two herringbone-shaped grooves 71 a and 71 bwhich extend in different directions. The groove 71 a is longer than thegroove 71 b. The dynamic pressure generated in the dynamic-pressuregenerating grooves 71 forms a sealing liquid film between therotary-side bearing 28 a and the fixed-side bearing 28 b and deliversthe sealing liquid toward the oil seal 41. The delivered sealing liquidleaks little by little from between the oil seal 41 and the drivingshaft 26 so as to prevent blood from entering the driving section.

Therefore, the bearing 28 functions not only as a bearing but also as amicropump for supplying the sealing liquid to the oil seal in tinyamounts.

In FIG. 11 is shown another embodiment of the bearing 28 formed in itsouter surface with a pair of groups of dynamic-pressure generatinggrooves and a series of dynamic-pressure generating grooves 75. Thepaired groups of dynamic-pressure generating grooves 74 deliver sealingliquid in the opposite directions to form a sealing liquid film betweenthe rotary-side bearing 28 a and the fixed-side bearing 28 b. Thedynamic-pressure generating grooves 75 act to deliver the sealing liquidtoward the oil seal 41. The sealing liquid is supplied from the supplyport 73 to the portion between the dynamic-pressure generating grooves74 and 75.

A second embodiment of this invention will be described with referenceto FIG. 12. The motor housed in the driving section 5 in this embodimentis of an immersed type in a liquid so as to circulate a sealing liquid.

The space in the driving section 5 in this embodiment is filled with thesealing liquid, and the stator 32 and the rotor 33 of the motor areimmersed in the sealing liquid. In the proximal end portion of thedriving section 5 is formed a passage 55 which is connected to a sealingliquid bag 12 via a pipe 56. In this embodiment, the dynamic pressurebearings 35 and 36 do not perform sealing but act as pumps for supplyingthe sealing liquid in the driving section 5 toward the sealing liquidchamber 30.

In this embodiment, the sealing liquid circulates by the pump action dueto the dynamic pressure generated by the dynamic pressure bearings 35and 36 in such a manner that the sealing liquid is supplied from theinterior of the driving section 5 to the sealing liquid chamber 30 thento the sealing liquid bag 12 through the groove 37, the passage 38 andthe pipe 11 and returns to the interior of the driving section 5 throughthe pipe 56 and the passage 55.

Since the interior of the driving section 5 of this embodiment is filledwith the sealing liquid, motor resistance increases. However, it isunnecessary to consider damage if the sealing liquid enters the drivingsection 5 in this embodiment as it does in the first embodiment, leadingto an easy design and enhancing reliability. Because of the circulationof the sealing liquid, the liquid carries heat generated in the statorcoil 32 of the motor or the like to the sealing liquid bag such that theheat can be dissipated in the human body in a dispersed manner. Thus,the temperature of the sealing liquid and the driving section 5 ismaintained substantially as high as the temperature of the human body.It is unnecessary, therefore, to consider the possibility oflow-temperature damage even if the temperature of the surface of thedriving section 5 rises more than the temperature of the human body.This makes the design consideration for heat radiation of artificialhearts simple and enhances its reliability. The other structures of thesecond embodiment are the same as those of the first embodiment. Theparts and elements of the second embodiment which are the same as thoseof the first embodiment are designated by the same reference numeralsand the description thereof is omitted.

A third embodiment of this invention is shown in FIGS. 13 and 14.Similar to the second embodiment as shown in FIG. 12, the artificialheart of this embodiment circulates a sealing liquid through the mainbody of the artificial heart and a sealing liquid bag 12. The sealingliquid flows from the supplying port 55 formed in the rear end portionof the driving section 5 into the main body of the artificial heart andthen flows out from the vicinity of the sealing mechanism 31 into thesealing liquid bag 12. In this way, the sealing liquid is circulated. Inthis embodiment, therefore, the sealing liquid circulates in the overallmain body of the artificial heart, whereby the interior of the main bodyis always maintained clean, leading to high reliability.

A filter 80 is provided in the sealing liquid bag 12, for removingforeign matter contained in the sealing liquid returned from the mainbody of the artificial heart such that the sealing liquid is alwaysclean. The sealing liquid bag 12 is provided with a liquid therapy port81 through which the sealing liquid is supplemented or replaced.

FIG. 14 is an enlarged partial view of the sealing mechanism 31 of themain body of the artificial heart of this embodiment. A pair of groupsof dynamic pressure grooves 82 and 83 are formed in the outer peripheralsurface of the rotary-side bearing 28 a of the bearing assembly 28. Onegroup of dynamic pressure grooves 82 are longer in the axial directionthan the other group of dynamic pressure grooves 83 such that the formergroup delivers more sealing liquid than the other group. With thisstructure, therefore, the sealing liquid is sent in opposite directionsby the dynamic pressure grooves 82 and 83 and a sealing liquid film isformed between the rotary-side bearing 28 a and the fixed-side bearing28 b due to dynamic pressures in the dynamic pressure grooves 82 and 83.Since the former group of dynamic pressure grooves 82 deliver moresealing liquid than the latter group of dynamic pressure grooves 83 do,the sealing liquid is supplied toward the oil seal 41.

When the sealing liquid which is being sent toward the oil seal 41passes through the orifice portion 84, the flow speed of the liquidincreases and is sent to a rear side portion of the oil seal 51. Vaneprojections 85 are formed on the portion of the driving shaft 26 whichis close to the oil seal 41. As the driving shaft 26 rotates, the vaneprojections 85 agitate the sealing liquid therearound and deliver it tothe rear side portion of the oil seal 41. As a result, neither thesealing water nor foreign matter stay in the rear side portion of theoil seal 41, whereby sealing of the oil seal 41 is securely maintained.

In the wall of the extension 24 of the casing 21 of the main body of theartificial heart is formed an exhaust passageway 81 through which thesealing liquid in the rear side portion of the oil seal 41 is sent tothe sealing liquid bag 12.

In FIGS. 15 to 17, a fourth embodiment of the present invention isshown. In the fourth embodiment, mechanical seals are applied to thesealing mechanism of the driving shaft. While in the previousembodiment, oil seals are used for the sealing mechanism of the drivingshaft, the fourth embodiment employs mechanical seals to enhance itsdurability.

The fourth embodiment is almost the same as the above describedembodiment except for the sealing mechanism and its related portions.Specifically, in FIG. 15 numeral 105 indicates a driving section, and104 denotes a pump section. As in the previous embodiment, the pumpsection 104 is inserted into the left ventricle B via a cardiac apexring 2.

In the driving section 105, a motor 106 is provided. The motor 106 is acanned motor where a rotor is housed in a casing filled with liquid.Numeral 107 indicate a stator coil and 108 a rotor the spacing betweenthe rotor 108 and the casing, or an air gap 109 is designed to allow asealing liquid such as used in the previous embodiment to circulate inthe driving section 105, a sealing liquid inlet 110 and a sealing liquidoutlet III are made. They are connected to a seal liquid bag 112 viaflexible circulation tubes 1-14, 115, respectively. Then, the sealingliquid circulates between the sealing liquid bag 112 and the inside ofthe artificial heart. In the sealing liquid bag 112, there is provided afilter, which removes foreign matter mixed in the circulating sealingliquid.

The pump section 104 contains a thin-wall, cylindrical tube section 120and a casing section 121 formed at the tip portion of the tube section.In the casing section 121, a pump rotor composed oil a rotor boss 123and a plurality of rotor blades 124 provided on the boss so as toproject from around the boss is housed. The pump rotor is rotated by themotor 106. Numeral 128 indicates a spinner that provides flowstraightening in the casing section 121; there are a plurality of statorvanes 125 and a plurality of front stator vanes also serving as a stayfor the casing section 121.

On the base end side of the casing section 121, a fluid inlet 127 ismade, through which the blood in the left ventricle of the heart issucked. The blood is discharged from the distal end of a nozzle section122. The nozzle section 122 is inserted in the aorta through the aortavalve of the heart.

The number of the stator vanes 125, 126 and that of rotor blades 124 areset at values that do not contain the common factors or integralmultiples of the common factors, that is, at prime factors with respectto each other, which thereby prevents the resonance or pulsation ofblood sent by rotation of the rotor blades 124.

Explained next will be the driving shaft of the artificial heart and itssealing mechanism in the present embodiment. In FIG. 15, numeral 130indicates a driving shaft. The base end portion of the driving shaft 130is connected to the rotor 108 of the motor 106. The tip end portion ofthe shaft is connected integrally to the rotor boss 123 of the pumprotor, which is driven via the driving shaft 130. In the tube section120 of the pump section 104, a cylindrical bearing tube 131 is housed.The driving shaft 130 is inserted in the bearing tube 131.

At the tip portion of the bearing tube 131, a mechanical sealingmechanism 132 acting as a sealing mechanism is provided. The mechanicalsealing mechanism 132 prevents the blood in the left ventricle of theheart from entering the inside the artificial heart.

The construction of the mechanical sealing mechanism 132 will bedescribed with reference to FIGS. 15 to 17. At the tip portion of thebearing tube 131, a flange-like fixed-side seat ring 133 is formed. Theend of the seat ring 133 is machined precisely so as to have a smoothsurface perpendicular to the rotation axis of the driving shaft 130 andprovides a sealing surface. A rotary-side follow ring 134 is in closecontact with the sealing surface of the seat ring 133 so as to rotatefreely, thereby maintaining the seal. The follow ring 134 has a diskshape and is provided integrally at the tip portion of the driving shaft130 so as to be precisely perpendicular to the rotation axis of thedriving shaft.

Furthermore, at the base end portion and tip portion of the drivingshaft 130, bearing sections 135 and 136 are integrally formed,respectively. These bearing sections 135, 136 are cylindrical andsupported by the inner surface of the bearing tube 131 so as to rotatefreely. The outer surface of these bearing sections 135, 136 and theinner surface of the bearing tube 131 are machined precisely. Thesebearing sections 135, 136 and bearing tube 131 support the driving shaft130 precisely so as to rotate freely.

As shown in FIG. 17, spiral shallow dynamic-pressure grooves 140 aremade in the outer surface of these bearing sections 135, 136. Thesedynamic-pressure grooves 140, when the driving shaft 130 rotates,introduces the sealing liquid into the spacing between the outer surfaceof these bearing sections 135, 136 and the inner surface of the bearingtube 131, thereby assuring lubrication between them, and allows thesealing liquid to flow toward the tip portion at a specific rate.Therefore, these bearing sections 135, 136 and bearing tube 131constitute a one-way dynamic-pressure bearing that functions as both abearing for supporting the driving shaft 130 and a pump for feeding thesealing liquid. Furthermore, the driving shaft 130 is not restricted inthe direction of the axis with respect to the bearing tube 131, but canmove freely in the axis direction. In the driving section 105, aring-shaped permanent magnet 146 is provided on the fixed-side of thehousing of the driving section. A ring-shaped permanent magnet 146 isalso provided on the rotor 108 of the motor 106, that is, on the drivingshaft 130 side. These permanent magnets 145, 146 face each other with aspecific distance between them. The polarity of these permanent magnets145, 146 is set so that they may repel one another in the axisdirection. The repulsion of these permanent magnets 145, 146 actuatesthe driving shaft 130 so that the shaft may move toward the base end,thus pressing the follow ring 134 on the driving shaft 130 against theseat ring 133, thereby maintaining the sealing effect of the mechanicalsealing mechanism 132.

The spacing between the bearing tube 131 and the driving shaft 1-30 isdesigned to act as sealing liquid chambers 137, 138 through which thesealing liquid circulates. The sealing liquid chamber 138 is isolatedfrom the outside, that is, the blood passageway in the left ventricle ofthe heart, by the mechanical sealing mechanism 132. thereby maintainingthe seal.

In the outer portion of the tube section 120 of the pump section 104, acirculation passage 142 is made. The tip portion of the circulationpassage 142 is connected to the sealing liquid chamber 138 and its baseend portion is connected to the sealing liquid outlet 111. Therefore,the sealing liquid flows from the sealing liquid bag 112 through thecirculation tube 114 and sealing liquid inlet 110 into the air gap 109of the motor 106. Then, by the pumping action of the one-waydynamic-pressure bearing composed of the bearing sections 135, 136 andbearing tube 131, the sealing liquid is sent, through the sealing liquidchambers 137, 138 toward the back of the mechanical sealing mechanism132 at a specific pressure. The sealing liquid fed to the sealing liquidchamber 138 is returned to the sealing liquid bag 112 via thecirculation passage 142, sealing liquid outlet 111, circulation tube115, and filter 113, and circulates in this route.

The function and advantage of the fourth embodiment described above areas follows. First, with the one-way dynamic-pressure bearings 135, 136feed the sealing liquid to the sealing liquid chamber 138 at a specificpressure. The sealing liquid forms a thin film of 0.5 to 1.0 mm inthickness between the seat ring 133 of the mechanical sealing mechanism132 and the sealing surface of the follow ring 134. The thin filmeffects lubrication and sealing between the seat ring and the followring. This prevents blood from entering the sealing liquid chamber 138,or the inside of the artificial heart.

When the artificial heart is actually used, protein in the blood, butonly a little may enter due to diffusion. This protein is coagulated byheating due to the sliding friction between the seat ring and followring that rotate relatively with respect to each other. Particles of thecoagulated protein are discharged outward under the influence of thecentrifugal force of the follow ring 134 that is rotating, and arewashed away by the blood flowing outside the mechanical sealingmechanism. The particles of the coagulated protein are so small thatthey have no adverse effect on the human body even if diffused into theblood.

Although the coagulated protein may adhere at the inner peripheral edgeportions of the seat ring 133 and follow ring 134, such proteinparticles will be washed away by the sealing liquid circulating insidethe mechanical sealing mechanism 134, or inside the sealing liquidchamber 138. These protein particles are captured by the filter 113 inthe sealing liquid bag 112, so that the sealing liquid will not becontaminated.

The fourth embodiment using the mechanical sealing mechanism as thesealing mechanism has the following advantages, as compared with theprevious embodiment using an oil seal as the sealing mechanism.

Although an oil seal has a simple structure and keeps well in closecontact with the driving shaft, when protein in the blood diffusesbetween the oil seal and the peripheral surface of the driving shaft andcoagulates there, the coagulated protein will not be discharged bycentrifugal force as described above because the oil seal is in contactwith the peripheral surface of the driving shaft. Furthermore, since theoil seal is highly flexible, when coagulated protein deposits betweenthe peripheral surface of the driving shaft and the oil seal, theinternal diameter of the oil seal extends easily, increasing the spacingbetween the peripheral surface of the driving shaft and the oil seal.This increase in the spacing increases the flow rate of the sealingliquid flowing outside through the spacing. The flow of the sealingliquid washes away the coagulated protein into the blood, resulting inan increase in the amount of sealing liquid flowing outside, or theconsumption of the sealing liquid. Because of this it is necessary tofrequently supply additional sealing liquid to the sealing liquid bag,imposing a heavier burden on the patient.

In contrast, with the mechanical sealing mechanism, centrifugal forcedischarges the coagulated protein as described earlier, so that thespacing between the seat ring and the follow ring is constantly keptnarrow. As a result, the volume of sealing liquid flowing outside issmaller and consequently the frequency of adding the sealing liquid islower, easing the burden on the patient.

In addition, the sealing liquid circulated as described above cools themechanical sealing mechanism 132, effectively preventing part of themechanism from being locally heated to high temperatures due to slidingfriction. This prevents the blood cells from being destroyed as a resultof the blood touching high-temperature portions.

In addition, a mechanical seal is more durable than the oil seal,because the seat ring and follow ring are made of ceramic material ormetal material.

In the above embodiment, the bearing tube 131 and driving shaft 130defining the mechanical sealing mechanism are preferably formed of fineceramic material, and the follow ring 134 is formed of graphitematerial. They are precision ground. The ceramic material is chemicallystable and superior in dimensional stability. In the present embodiment,the bearing tube 131 and the seat ring 133 as well as the driving shaft130 and the bearing sections 135, 136 are formed integrally, so that thedimensional accuracy of their assembly and the resulting mechanicalsealing mechanism are high. Consequently, the accuracy of the positionalrelationship, such as the perpendicularity or concentricity of the seatring 133 and follow ring 134 with respect to the rotation axis, is high,assuring a high reliability. Since the follow ring 134 is formed ofcarbon graphite, it matches the seat ring 133 well. Additionally, thegraphite, a form of carbon, has self-lubricating properties, and thecoefficient of friction is low.

The materials for these members are not restricted to what have beendescribed above, but may be suitable combinations of various types ofmaterials such as ceramic, graphite, composite materials, metalmaterials, and the like.

In the present embodiment, the follow ring 134 is pressed against theseat ring 133 in the mechanical sealing mechanism 132 by magneticrepulsion of the permanent magnets 145, 146, resulting in a simplerconfiguration and higher reliability. The urging pressure may come fromattraction between the permanent magnets.

FIGS. 18 and 19 show a fifth embodiment of the present invention. Thefifth embodiment is the same as the fourth embodiment except for part ofthe mechanical sealing mechanism and part of the circulation route ofthe sealing liquid.

Specifically, in the fifth embodiment, a driving shaft 230 and bearingmembers 235, 236 are formed into separate members. The bearing member235 on the base end side is supported by a bearing sleeve 240, and thebearing member 236 on the tip end side is supported by a short bearingtube 231. On the bearing member 235 on the base end side, a flangesection 243 is formed, thereby constituting a thrust bearing.

Between the outer surface of the bearing sleeve 240 and the housing ofthe driving section 5, a passageway 241 is formed. A passageway 242 isalso formed between the inner surface of the bearing section 236 on thetip end side and the driving shaft 230. The sealing liquid passesthrough these passageways and circulates through the sealing liquidchambers 137, 138. In the present embodiment, a sealing liquidcirculating pump 250 is provided. Outside the body or inside theabdominal cavity of the patient, and the pump 250 circulates the sealingliquid.

At the tip end portion of the bearing tube 231, is an integrally formedflange-like seat ring 133. The follow ring 134 is in close contact withthe sealing surface of the end of the seat ring 133. The follow ring 134is a member separate from the driving shaft 230. The follow ring 134 isinstalled on the rotor boss 223 of the pump rotor. The rotor boss 223 isdesigned to move freely a specific distance in the axis direction withrespect to the driving shaft 230. The follow ring 134 can move to someextent in the axis and the diameter direction with respect to thedriving shaft 230. An O ring provides sealing between the follow ring134 and the driving shaft 230.

The rotor boss 223 is hollow and houses a pair of disk-shaped permanentmagnets 263, 264 in it. One permanent magnet 263 is mounted on the rotorboss 223 and the other permanent magnet 264 is mounted on tile drivingshaft 230. The polarity of these permanent magnets 263, 264 is set sothat they may repel each other. The force of repulsion presses thefollow ring 134 against the end of the seat ring 133.

In the present embodiment, the driving shaft 230, rotor boss 233, andfollow ring 134 can move independently from each other. A relativemovement between them can absorb vibrations caused by their rotation.This enables the follow ring 134 to be pressed against the end of theseat ring 133 more stably, resulting in an increase in the reliabilityof the mechanical sealing mechanism 132.

In this embodiment, because the sealing liquid is circulated by thesealing liquid circulating pump 250, the circulating flow rate andpressure of the sealing liquid can be regulated freely.

FIG. 20 shows a sixth embodiment of the present embodiment. In the sixthembodiment, the follow ring 134 is pressed against the seat ring 133 bya compression coil spring 270 in place of the pair of permanent magnets263, 264 in the fifth embodiment. The sixth embodiment has the sameconfiguration as that of the fifth embodiment except as stated above. InFIG. 20, the parts corresponding to those in the fifth embodiment areindicated by the same reference symbols and explanation of them will notbe given.

The present invention can be applied to an artificial heart having acentrifugal pump. Hereinbelow, we will explain embodiments of anartificial heart comprising a pump section consisting of a centrifugalpump and a mechanical seal mechanism.

FIG. 21 shows the state of an artificial heart having a centrifugal pumpembedded in a body cavity. To describe more specifically, the main body303 of the artificial heart is constituted of a pump section 304consisting of a centrifugal pump and a driving section 305 accommodatinga motor therein. The main body 303 is embedded in the body cavity and onthe outside of the heart.

Onto the pump section 304, an entrance nozzle 327 is provided. Tocardiac apex C of heart A, a cardiac apex ring 302 is fitted. Theentrance nozzle 327 is inserted into a left heart ventricle B by way ofthe cardiac apex ring 302.

To an exit nozzle 322 of the pump section 304 is connected an artificialblood vessel 360, which is connected to aorta G without passing throughthe left ventricle B. The artificial vessel 360 is connected to aorta Gby suture.

To the main body 303 is connected a supply tube 361, which is guided outof the body cavity via appropriate means. In the supply tube 361 areaccommodated a tube for circulating a sealing liquid and an electricwire for driving a driving section 305. The sealing liquid is circulatedby way of the main body 303 by a sealing liquid supply unit (not shown).Power is supplied to the driving section from an outside electric sourcevia the electric wire.

In the artificial heart having the aforementioned structure, the bloodof the left ventricular B is first sucked by the pump section 304 by wayof the entrance nozzle 327, pressurized by the pump section 304, passedthrough the artificial blood vessel 360 via the exit nozzle 322, and fedinto aorta G without passing through the left ventricular B and a mitralvalve. The artificial heart serves for supplying blood to aorta Gwithout disturbing the natural heart beat in order to make up forshortage in blood supplied only by the natural heart beat.

FIG. 22 shows a main body 303 of the artificial heart having acentrifuge pump according to a seventh embodiment, shown in FIG. 21. Themain body 303 is constituted of the pump section 304 consisting of acentrifugal pump and a driving section 305. In the pump section 304, animpeller 324 is provided. A reference numeral 328 indicates a spinner.To the pump section 304 is provided an entrance port 326, to which theentrance nozzle 327 is further provided. The pump section includes anexit port 322, to which an end portion of the artificial vessel 360 isconnected.

The driving section 305 houses a motor 306 having an driving shaft 330.The top end portion of the driving shaft 330 is inserted into the pumpsection 304, thereby being connected to the impeller 324. Referencenumerals 307, 308, and 309 are a stator, rotor, and electric wire forsupplying power to the motor, respectively.

In the driving portion 305 are disposed a scaling liquid inlet 310 and asealing liquid outlet 311, by way of which the sealing liquid iscirculated through the driving section 305.

To the portion in which the driving shaft 330 is just inserted into thepump section 304 is provided a mechanical seal mechanism 332, whichprevents blood passing through the pump section 304 from entering intothe driving section 305. To the casing side of the driving section 305and to the rotor-side of the motor 306, a pair of permanent magnets 345and 346 are respectively provided so as to be opposed to each other.Attractive force generated between permanent magnets 345 and 346 isloaded on the driving shaft 330 in the lengthwise direction thereof, andconsequently the force is added onto a portion between a seat ring and afollow ring of the mechanical seal mechanism 332 in the lengthwisedirection, maintaining sealing between these rings. The sealing liquidis circulated through the mechanical seal mechanism 332 to ensure asealing tightness and simultaneously to cool the mechanical sealmechanism 332.

FIG. 23 shows the main body 303 of the artificial heart of an eighthembodiment of the present invention. The main body of this embodimenthas substantially the same structure as that of the seventh embodimentof the present invention except that permanent magnets 345 and 346 arearranged so as to provide load to the driving shaft 330 in thelengthwise direction by repulsion force thereof. To avoid repetitions inFIG. 23, like reference numerals designate like structural elementsexplained in FIG. 22 showing the seventh embodiment.

FIG. 24 shows the mechanical seal mechanism 332 of a ninth embodimentfor use in the artificial hearts having a centrifugal pump of theseventh and eighth embodiments. The mechanical seal mechanism 332 ischaracterized in that a follow ring 334 of a flange form is providedonto the top of a driving shaft 360 and in that a cylindrical shaftbearing section 335 is formed so as to be integrated with the followring 334. Furthermore, the periphery of the integrated structure iscovered with a cylindrical seat ring 333, which is provided to thecasing of the driving section 305 and the like. The upper surface of theseat ring 333 is tightly connected to the lower surface of the followring 334, thereby constructing the mechanical seal mechanism. The innerperiphery of the seat ring 333 supports the seat bearing section 335 insuch a way that the section 335 can be rotated freely. in this way, theseat bearing mechanism is constructed.

Between the seat ring 333 and the shaft bearing section 335 is formed asealing liquid passage 370 of a ring-form. On the lateral side of theseat ring 333 is formed a sealing liquid flow-in port 371. On theopposite side of the flow-in port 371 is formed a sealing liquidflow-out port 372.

In the mechanical seal mechanism of the embodiment 8, the seat ring 333is made of a ceramic material. On the other hand, the follow ring 334and the shaft bearing section 335 are made of a carbon compositematerial.

The sealing liquid circulating through the driving section 305 issupplied from the sealing liquid flow-in port 371 into the sealingliquid passage 370, flows through the passage 370, and goes out from thesealing liquid flow-out port 372. The flow of the sealing liquid ensuresthe sealing tightness between the seat ring 333 and the follow ring 334,thus preventing blood of the pump section 304 from flowing into thedriving section 305. On the other hand, the flow of the sealing liquidcools the seat ring 333 and the follow ring 334, thus preventingtemperature elevation taken place in the sealing portion. Successfulsuppression of temperature elevation makes it possible to preventcoagulation of blood proteins taken place in a narrow interspace of thesealing portion. As a result, the sealing tightness is ensured and theseat ring 333 is prevented from adhering to the follow ring 334.

To prevent coagulation of blood proteins as mentioned above, it iseffective to reduce the temperature of a lubricating thin film of thesealing liquid to 50° C. or less which is present between the seat ring333 and the follow ring 334. This is because if the temperature of thelubricant thin film is suppressed to 50° C., or less, the coagulation ofblood components in the space between the seat ring 333 and the followring 334 can be securely prevented since the mostcoagulation-susceptible component of the blood, namely, fibrinogen, isdenatured by heat of about 50° C.

The temperature can be reduced by controlling the flow amount of thesealing liquid flowing through the sealing liquid passage 370. If anexcessive amount of the sealing liquid is used, the sealing liquidpassing through the sealing portion and flowing into the pump section304 is increased in amount. As a result, the sealing liquid will beconsumed in a large amount and should be supplied more frequently. Thisresult is not preferable since a patient receives a great burden, Forthe reasons mentioned above, it is important to set the flow amount ofthe sealing liquid at a minimum and sufficient amount required forcontrolling the temperature of the lubricating thin film to 50° C.—orless.

In practice, it may be preferred to perform a test using an. artificialheart and determine the minimum and sufficient amount of the sealingliquid based on the experimental results obtained in the test. Since theartificial heart is embedded in a body when used, the peripheraltemperature of the artificial heart is equal to the body temperature. Itwill be therefore easy to determine the minimum and sufficient flowamount to be needed if the experiment can be carried out undertemperature as constant as the body temperature.

If the sealing portion between the seat ring 333 and the follow ring 334can he further cooled by a different method other than theaforementioned cooling method employing a sealing liquid, the minimumand necessary flow amount can be set to a further smaller value. Forexample, it is effective to increase surface area to be exposed to thesealing liquid or blood by making the sealing surface in the form offlange. Alternatively, the following method is effective. The spinner328 is formed solid by using highly heat conductive metal material andbrought into contact with the upper surface of the follow ring 334. Ifthe spinner 328 thus constructed is used, heat can be released intoblood through the spinner 328 by means of heat conduction.

There are various preferable embodiments of mechanical seal mechanism332 other than those introduced in the above. In a tenth embodiment ofthe mechanical seal mechanism 332 shown in FIG. 25, a follow ring 334 isformed independently of the shaft bearing section 335. The sealingliquid passage 373 surrounding the driving shaft 360 is formedtherebetween. The follow ring 334 may be formed of a material differentfrom that forming the shaft bearing section 335. For example, the followring 334 is formed of a carbon composite material to impart lubricityand to ensure sealing tightness; on the other hand, the shaft bearingsection 335 is formed of a ceramic material to improve durability. Thetenth embodiment has the same structure as that of the ninth embodimentshown in FIG. 9 except for the aforementioned respects. To avoidrepetitions in FIG. 25, like reference numerals designate likestructural elements explained in FIG. 24 showing the ninth embodiment.

In an eleventh embodiment of the mechanical seal mechanism 332 shown inFIG. 26, between a follow ring 334 and a spinner 32 is interposed abumping material 373 formed of elastic material, e.g., ethylenepropylene diene monomer (EPDM). The follow ring 334 is capable of movingin the lengthwise direction and diameter direction of a driving shaft360. By virtue of this structure, if the driving shaft 360 is vibrated,the vibration will be adsorbed by the bumping material 373, preventingthe vibration of transmitting to the follow ring 373. In this mechanism,the follow ring 334 can be connected tightly and securely to a seat ring333, ensuring sealing tightness.

In the eleventh embodiment, a sealing-liquid introducing passage 374 isformed in the center portion of the driving shaft 360 along thelengthwise direction. The sealing-liquid introducing passage 374 isopened in the periphery surface to communicate with a sealing liquidpassage 370. The sealing liquid therefore blows out from the opening ofthe sealing liquid introducing passage 374, and impinges upon thesealing portion of the follow ring 334 and the seat ring 333. on theother hand, the sealing liquid is turned around in the sealing liquidpassage 374 when a rotation shaft 360 is rotated. By virtue of thesestructural features, the sealing portion can be efficiently cooled.

The eleventh embodiment has the same structure as that of the tenthembodiment except for the aforementioned respects. To avoid repetitionsin FIG. 26, like reference numerals designate like structural elementsexplained in FIG. 25 showing the tenth embodiment.

In the twelfth embodiment of the mechanical seal mechanism shown In FIG.27, a head section 375 is provided onto the top of a driving section360. A bumping material 373 is interposed between the head section 375and a follow ring 334. The twelfth embodiment has the same structure asthat of the eleventh embodiment except for the aforementioned respects.To avoid repetitions in FIG. 27, like reference numerals designate likestructural elements explained in FIG. 26 showing the eleventhembodiment.

The mechanical seal mechanisms according to the ninth to twelfthembodiments respectively shown in FIGS. 24 to 27 are suitable for thesealing mechanism for an artificial heart having a centrifugal pumps asdescribed in the seventh and eighth embodiments shown in FIGS. 22 and23. Furthermore, application of these mechanical seal mechanisms may notbe limited to the artificial heart having a centrifugal pump. Themechanical seal mechanisms may be, of course, applied to an artificialheart having an axial-flow pump as shown in FIG. 15 or 18.

In a thirteenth embodiment of the artificial heart having a centrifugalpump, shown in FIG. 28, a pump section 304 is formed so as to beintegrated with an introducing nozzle 427 for introducing blood. Theintroducing nozzle 427 is bent along the shape of the left ventricle.

FIG. 29 shows the structure of a fourteenth embodiment of the mechanicalseal mechanism 332 suitable for use in the artificial heart according tothe thirteenth embodiment shown in FIG. 28. The fourteenth embodimentemploys a bumping material 373 having a cross-section of an invertedU-letter form. The bumping material 373 covers an outer peripheralsurface, upper surface and inner peripheral surface of a follow ring334. Since bumping effect can be improved by the bumping material thusarranged, it is possible to reduce the bumping material 373 inthickness. Consequently, an entire size of the mechanical seal mechanism332 can be reduced.

In this embodiment, since the seal liquid inlet 371 is opened upwardlyin the diagonal direction, a flowing-in sealing liquid is directly hitupon the sealing portion, cooling it more effectively. The fourteenthembodiment has the same structure as that of the tenth embodiment shownin FIG. 25 except for the aforementioned respects. To avoid repetitionsin FIG. 29, like reference numerals designate like structural elementsexplained in FIG. 25 showing the tenth embodiment.

The application of the mechanical seal mechanism according to thefourteenth embodiment shown in FIG. 29 is not limited to the artificialheart having a centrifugal pump mentioned above. It may be, of course,used in the artificial heart having an axial-flow pump mentioned above.

In both the fifth and sixth embodiments of FIGS. 19 and 20, the drivingshaft 230 mounts a pin 262 (illustrated only in FIG. 19) which engages arecess in the follower ring 134. Consequently, upon rotation of drivingshaft 230, the rotor boss 223 and associated parts including hollow ring134 rotate in response to rotation of driving shaft 230.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, and representative devices shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. An artificial heart for embedding in a heart of ahuman body comprising: a casing including first and second inlet ports,first and second outlet ports, a first passage defined in the casing andin communication with said first inlet and outlet ports, and a secondpassage defined in the casing and in communication with said secondinlet and outlet ports; a first pump mechanism provided in said firstpassage; a driving mechanism for driving said first pump mechanism sothat blood is sucked at the first inlet port, flows through the firstpassage and is discharged from the first outlet port, said drivingmechanism including a driving shaft and a motor for rotating the drivingshaft; a sealing mechanism provided between the first and secondpassages to seal the first passage against the second passage so thatblood flowing through the first passage is prevented from entering inthe second passage, the sealing mechanism being exposed to the firstpassage, said sealing mechanism including a movable seal member attachedto the driving shaft and having a first seal surface, and a stationaryseal member having a second seal surface, and further including meansfor urging the driving shaft to make the first seal surface contact thesecond seal surface to define a boundary therebetween; a third passagein communication with said second inlet and outlet ports; and a secondpump mechanism for circulating a sealing liquid between the second andthird passages to make the sealing liquid contact the sealing mechanism.2. The artificial heart according to claim 1 wherein said casingincludes a pump section provided on one side thereof and housing thefirst pump mechanism therein, and a driving section provided on theother side of the casing and housing the driving mechanism, and whereinsaid first inlet and outlet ports are arranged on the pump section, andsaid second inlet and outlet ports are arranged on the driving section.3. The artificial heart according to claim 2 wherein said driving shaftextends to the pump section from the driving section and wherein saidfirst pump mechanism includes an impeller attached to the driving shaft.4. The artificial heart according to claim 1 wherein said movable sealmember includes a seal ring coaxially attached to the driving shaft, theseal ring having one surface provided with a central recess therein andan annular peripheral area defining said first seal surface, and saidstationary seal member includes a mating ring having an annular surfacedefining said second seal surface.
 5. The artificial heart according toclaim 4, wherein each of the first and second seal surfaces is a flatsurface.
 6. The artificial heart according to claim 1 wherein said firstpump mechanism includes a centrifugal pump.
 7. The artificial heartaccording to claim 1 which comprises a flexible tube define said thirdpassage therein, and wherein said second pump mechanism includes a pumpprovided on the flexible tube.
 8. The artificial heart according toclaim 7 which comprises a container for storing the seal liquid therein,provided on the flexible tube.
 9. The artificial heart according toclaim 8 which comprises a filter provided on the flexible tube, forremoving foreign matter in the sealing liquid circulating between secondand third passages.
 10. The artificial heart according to claim 9wherein said filter is mounted on the container.
 11. The artificialheart according to claim 1 which includes a filter for removing foreignmatter in the sealing liquid circulating between second and thirdpassages.